Reciprocating means



Jan. 7, 1964 L. KRAMER 4 RECIPROCATING MEANS Filed Aug. 5, 1962 3 Sheets-Sheet 1 INVENTOR LEO KRAMER l HIS ATTORNEY Jan. 7, 1964 L. KRAMER RECIPROCATING MEANS 3 Sheets-Sheet 2 Filed Aug. 5, 1962 K-Ir lNVENTOR LEO KRAMER BY I I" HIS ATTORNEY United States Patent 3,116,698 RECIPRGCATING MEANS Leo Kramer, Athens, Pa., assignor to ln ersoll-ltand Comparry, New York, N.Y., a corporation of New Jersey Filed Aug. 3,1962, Ser. No. 214,593 17 Claims. (Cl. 103-162) The present invention relates to fluid pumps and motors and more particularly to an improved reciproeating means for a piston of such pumps and motors.

Heretofore, the reciprocating pistons in the barrel of a fluid pump or motor usually have been sliadbly engaged and rode on a thrust plate or wobble plate, which thrust plate is tilted at an angle other than a right angle with respect to the rotary axis of the barrel. The stroke of the pistons is adjusted and varied by changing the tilt angle of the thrust plate. A disadvantage in this type of construction is that the slidable engagement between the ends of the pistons and the thrust plate provides relatively large friction losses, particularly at low rotary speeds of the barrel, thus lowering low speed performance of the pump or motor. Also, the mechanism for tilting the thrust plate to different angles relative to the barrel axis, to vary the stroke of the pistons must be relatively strong and is also complicated.

In this conventional reciprocating mechanism for the reciprocating pistons of a pump or motor, the displacement of such pistons is proportional to the tangent of the tilt angle of the thrust plate. In addition, the reaction of the thrust plate against the piston produces side forces between the piston and its bore. This makes for considerable wear and frictional losses particularly at low speeds. The conventional thrust plate is therefore given a large mass to reduce vibration.

Conventional reciprocating mechanisms for reciprocating the pistons of a fluid pump or motor are of the type shown in U.S. Patent No. 1,483,199, issued Feb. 12, 1924, to A. Schinkez; U.S. Patent No. 1,487,965, issued Mar. 25, 1924, to A. G. M. Michell; U.S. Patent No. 2,389,186, issued Nov. 20, 1945, to A. Y. Dodge; U.S. Patent No. 2,445,281, issued July 13, 1948, to C. H. Rystrom; U.S. Patent No. 2,475,770, issued July 12, 1949, to J. Wisjman; U.S. Patent No. 2,545,929, issued Mar. 20, 1951, to E. Orashansky, In; U.S. Patent No. 2,633,104, issued Mar. 31, 1953, to J. A. Lauck et al.; U.S. Patent No. 2,633,104, issued Mar. 31, 1953, to I. A. Lauck et al.; U.S. Patent No. 2,679,139, issued May 25, 1954, to C. A. Possum; U.S. Patent No. 2,741,423, issued April 10, 1956, to A. A. Lombard; U.S. Patent No. 2,792,789, issued May 21, 1957, to W. J. Mizen; U.S. Patent No. 2,8393%, issued June 17, 1958, to H. Stansfield et al.; U.S. Patent No. 2,847,261, issued Aug. 12, 1958, to R. T. Cornelius; U.S. Patent No. 2,913,911, issued Nov. 24, 1959, to I. E. Gilkey; U.S. Patent No. 2,920,488, issued Ian. 12, 1960, to R. C. Savage; U.S. Patent No. 2,944,529, issued July 12, 1960, to G. Wiggermann; U.S. Patent No. 2,956,845, issued Oct. 18, 1960; and U.S. Patent No. 2,990,784, issued July 4, 1961, to G. A. Wahlmark.

It is the general object of the present invention to avoid and overcome the foregoing and other difiiculties of and objections to prior art practices by the provision of an improved reciprocating means or mechanism, for reciprocating a piston of a pump or motor, which reciprocating mechanism eliminates the high friction losses between the ends of the piston and the thrust plate and provides a substantially frictionless engagement therebetween.

Another object of the present invention is the provision of an improved reciprocating mechanism which eliminates the side thrust on the piston thus reducing wear on the moving parts and permitting the use of a low mass thrust plate.

Yet another object of the present invention is the provision of an improved reciprocating mechanism which is readily positioned without the employment of associated complicated linkage.

A further object of the present invention is the provision of an improved reciprocating mechanism the linear movement of which (from one position to another position) is proportional to the piston displacement.

A still further object of the present invention is the provision of an improved reciprocating mechanism which is simple but rugged in structure.

Another object of the present invention is the provision of an improved reciprocating mechanism having less moving parts than conventional reciprocating mechanisms, thereby reducing the cost of initial fabrication and maintenance thereof.

The aforesaid objects of the present invention, and other objects which will become apparent as the description proceeds, are achieved by providing for a hydraulic pump or motor having housing means, a shaft rotatable with respect to the housing means, barrel means connected to the shaft and piston means reciprocable in the barrel means, and reciprocating means for reciprocating the piston means in the barrel means as the barrel means rotates. This improved reciprocating means comprises cage means disposed adjacent one end of the piston means and rotatable with the barrel means, thrust means on the housing means adjacent the cage means and defining with the cage means a cavity, the thrust means having cam means for reciprocating the piston in the barrel means, and rolling means in the cavity in contact with the piston means and the cam means. The thrust means is reciprocable with respect to the housing means to eccentrically dispose the cam means with respect to the barrel means and the shaft thus causing reciprocation of the piston means as the barrel means and the shaft rotate with respect to the housing means.

For a better understanding of the present invention reference should be had to the accompanying drawings, wherein like numerals of reference indicate similar parts throughout the several views and wherein:

FIG. 1 is a side elevational view of the improved reciprocating mechanism;

FIG. 2 is an enlarged longitudinal vertical sectional view of the improved reciprocating mechanism;

FIG. 3 is an enlarged side elevational view taken along the line 33 of FIG. 1 in the direction of the arrows, with the housing and nut removed for the sake of clarity;

PEG. 4 is a side elevational view of the barrel, cage and shaft;

FiG. 5 is a sectional View of the barrel taken along the line 55 of FIG. 4 in the direction of the arrows;

FIG. 6 is a sectional view of the cage taken along the line 6-6 of FIG. 4 in the direction of the arrows;

FIG. 7 is a side elevational View of the thrust member and nose piece;

FIG. 8 is an end view of the thrust member and nose piece taken along the line 88 of FIG. 7 in the direction of the arrows;

FIG. 9 is a fragmentary vertical sectional View of an alternative embodiment of the reciprocating mechanism;

FIG. 10 is a sectional view of a modified cage taken along the line 1tl1 in FIG. 9;

FIG. 11 is a view similar to FIG. 9 of another embodiment of the improved reciprocating mechanism;

FIGS. 12-14 are fragmentary sectional views similar to FIGS. 9 and 11 showing other forms of the cam surfaces;

FIG. 15 is a view similar to FIGS. 9 and 11 of a further alternative embodiment of the improved reciprocating mechanism; and

FIG. 16 is a fragmentary sectional view of an alternative construction of a piston.

Although the principles of the present invention are broadly applicable to all types of engines having a reciprocable piston, the present invention is particularly adapted for use in conjunction with fluid pumps and motors and hence it has been so illustrated and will be so described.

With specific reference to the form of the present invention illustrated in the drawings, and referring particularly to FIG. 1, a fluid pump is indicated generally by the reference numeral ltl. This improved fluid pump 10 has a housing means, such as a housing 12 and a casing nose 14. As shown in FIG. 2 an externally threaded port head 16 is secured against a shoulder 18 in the housing 12 by a nut 29, the inlet 22 and outlet 24 of such port head 16 (FIG. 3) being in communication with arcuate ports 26 in a stationary valve 28. This valve 28 is similar to the type shown in the above mentioned US. Patent No. 2,633,104. Seated against the stationary valve 23 is a barrel means, such as a barrel 3% (FIG. 2), which barrel 3%) is provided with bores 32 (FIG. having ports 34 and in which a like number of pistons 36 (FIG. 2) are reciprocated by the improved reciprocating mechanism of the present invention. In order to provide a drive means for the barrel 3t) a driving member, such as a shaft 38, is connected to the barrel 36 by a coupling means (of the type disclosed by me in US. application Serial No. 214,079, filed August 1, 1962, and entitled Coupling Means) or the key 55 (FIG. 2) and such shaft 38 is rotatable in bearing 42 carried by the casing nose 14.

For the purpose of biasing the stems 44 of pistons 36 beyond (i.e. to the right of as viewed in FIG. 2) the barrel 3t), a spring 45 is disposed in each bore 32 behind the associated piston 36.

Reciprocating Illechmzism The improved reciprocating means of the present invention for reciprocating the pistons 36 in the bores 32 of the barrel 39 has cage means, such as a cage 46 (FIGS. 2, 4 and 6), disposed adjacent the right end as viewed in FIG. 2 of the pistons 36 and is connected or keyed by a pin 48 (FIGS. 4, 5) projecting from the barrel 3:) into a dowel hole 50 in the cage 46 for rotation with the barrel 30. As shown in FIG. 2, the stems 44 of the pistons 36 are biased forwardly by springs 45 and project into apertures 52 (FIGS. 2 and 4) in the cage 46. It will be understood that the pin 48 and dowel hole 59 cooperate to align the bores 32 in the barrel 30 with the apertures 52 in the cage 46.

Thrust means, such as a stationary thrust plate 54 (FIGS. 2, 7 and 8), is diametrically reciprocable with respect to the casing nose 14 by means of pins 56 projecting from the thrust plate 54 into a diametrical slot 58 in the casing nose 14. This thrust plate 54 is thus disposed on the casing nose 14 adjacent the cage 46 and defines with the cage 46 and a bearing 59 on the shaft 33, a cavity 60. In order to provide for the reciprocation of the pistons 36 as the barrel 3% and shaft 38 rotate with respect to the thrust plate 54, rolling means, such as balls 62, are disposed in the cavity 69 in point contact with the pistons 36, the outer Wall of the apertures 52 in the cage 46, the external straight cam surface on the bearing 59 on the shaft 38 and cam means, such as the internal conical cam surface 64 provided in the thrust plate 54 (FIGS. 7 and 8).

In order to achieve true rotating action of the balls 62 in the cavity 69, either the bearing 59 or the cage 46 must rotate. In this case the cage 46 rotates with the barrel. The ball 62 rotates but does not roll in cavity 60. Since bearing 59 and cage 46 are both secured to shaft 38 they must rotate together. However, the outer race of bearing 59 is free to rotate relative to the cage 46 and therefore there is true rolling of the ball 62 on the straight cam surface of the outer race of bearing 59 and on the inner conical cam surface 64 of thrust member 54.

The thrust plate 54 is reciprocable with respect to the casing nose 14 of the housing means to eccentrically dispost the inner cam surface 64 with respect to the barrel 3!) and the shaft 38 thus causing reciprocation of the pistons 36 (by means of the balls 62) as the barrel 3t) and shaft 38 rotate with respect to the housing 12 and easing nose 14. The linear eccentricity of the thrust plate 54 with respect to the longitudinal axis of the barrel 3%) and shaft 33 is proportional to the displacement of the pistons 36, thus permitting calibration of the linear eccentricity. This reciprocating movement of the thrust plate 54 is in a plane through the axis of symmetry (axis AA FIG. 3) of the stationary valve 28.

In order to provide positioning means for positioning (and locking) the thrust plate 54 and the inner cam surface carried thereby in the desired position with respect to such longitudinal axis of the barrel 30 and shaft 38, positioning screws 66 (FIG. 2) are threadable into the housing 12 and are engageable with the thrust plate 54. This positioning means provides a simple device for increasing or decreasing the displacement of the pistons 36 thus eliminating the large mass heretofore required by conventional thrust plates to prevent wobble thereof.

It will be understood by those skilled in the art that the direction of rotation of the shaft 38 may be either clockwise or counterclockwise without changing the inlet or outlet porting. In other words, the motor can be reversed by merely shifting the thrust plate 54 to the opposite side of the axis of the shaft 33.

The conventional means of reversing a motor is by reversing the flow of oil through the motor. This tends to complicate the hydraulic circuitry because of the additional valving required. Also, the surge pressures and shock loads encountered during a sudden flow reversal are often dangerous. Further, additional hydraulic circuitry is required to overcome this danger.

In order to align the casing nose 14 with the axis AA (FIG. 3) of the stationary valve 28, a key 68 (FIG. 2) in the housing 12 projects into a keyway 70 in the casing nose 14.

It will be understood by those skilled in the art that alternative modifications can be made in the above described preferred embodiment of the improved reciprocat ing mechanism 10.

Alternative Embodiments In the hereinafter described alternative embodiments, similar parts throughout the various figures illustrating those embodiments are identified by the same number suffixed by letters a, b, c, d, e, f and g.

In order to use the fluid pump 10 as a fluid motor the eccentricity of the thrust plate 54 is reversed from an eccentricity below the longitudinal axis of the shaft 38 (FIG. 2) to an eccentricity above such longitudinal axis, with the shaft 38 still rotating in the direction of the arrow shown in FIG. 2.

As shown in FIGS. 9 and 10 a cage 46a may be formed integrally with a shaft 38a and provided with peripheral slots 72. The cavity 68a is formed between the outer or external conical cam surface 64a and the straight cam surface on an outer bearing 59a.

In FIG. 11 an outer bearing 5% may also be provided with an internal conical cam surface 641) thus providing double cam surfaces namely, external conical cam surface 64b on thrust plane 54!) and internal conical cam surface 64b on which a ball 6% may roll in substantially frictionless engagement.

As shown in FIGS. 12-14 other forms of the cam surfaces are the straight cam surface 640 on thrust plate 540 and inner conical cam surface 640 (FIG. 12) on hearing 59c; external convex arcuate cam surfaces 64d on thrust plate 54d and internal convex arcuate cam surface 64d on hearing 59d (FIG. 13); and external concave s,11e,ess

arcuate cam surfaces 64s on thrust plate 54c and internal concave arcuate cam surface 642 on bearing 5% (FIG. 14). These arcuate surfaces 64d, 650., 64s and 642 may be segments of paraboloids, ellipsoids or hyperboloids. The alternative embodiments of FIGS. 13 and 14 provide line contact rather than point contact between the balls 62d and 62e and the arcuate cam surfaces 640. and 64d and 64:2 and 64e respectively and the displacement of the pistons 36 is no longer proportional to the linear eccentricity of the thrust plates 54d (FIG. 13) and 54e (FIG. 14).

Alternatively, the balls 62, 62a, etc. may be replaced by rollers 74 (FIG. 15) having tapered or conical cam surfaces 76.

Further, as shown in FIG. 16, the ball 62g may be formed integrally with semi flexible shaft '77 carried by the piston 36g.

Referring to FIG. 2 it will be understood that the shaft 38 may project through the barrel 3% stationary valve 28 and port head 16.

it will be recognized by those skilled in the art that the objects of the present invention have been achieved by providing an improved reciprocating means or mechanism for reciprocating a piston of a fluid pump or motor, which reciprocating mechanism eliminates high friction losses between the stern of the piston and the thrust plate by providing substantially frictionless engagement therebetween. This novel reciprocating mechanism eliminates the side thrust on the piston thus reducing wear on the moving parts and allows the use of a thrust plate of reduced mass. This reciprocating mechanism is readily positioned to give desired piston displacement without the use of complicated associated linkage and mechanisms and is simple but rugged in structure. The reduced number of moving parts in this reciprocating mechanism reduces initial and maintenance costs thereof. Further, the linear movement of the thrust plate of this novel reciprocating mechanism is proportioned to the piston displacement thus providing calibration thereof.

While in accordance with the patent statutes preferred and alternative embodiments of the present invention have been illustrated and described in detail, it is to be particularly understood that the invention is not limited thereto or thereby.

I claim:

1. For a fluid device having housing means, a shaft rotatable with respect to said housing means, barrel means disposed about said shaft, and piston means reciprocable in said barrel means, reciprocating means for reciprocating said piston means in said barrel means, said reciprocating means comprising;

(a) cage means disposed adjacent one end of said piston means and connected to said barrel means,

([1) substantially conical cam means adjacent said cage means for reciprocating said piston means in said barrel means,

(0) bearing means disposed about said shaft and rotatable with respect thereto,

(d) said cage means, said substantially conical cam means, said bearing means and said piston means defining a cavity,

(e) said shaft being operatively associated with one of said barrel means and said substantially conical cam means to cause relative rotative movement between said barrel means and said substantially conical cam means, and

(i) rolling means in said cavity in rolling contact with said bearing means and said substantially conical cam means thereby substantially eliminating sliding friction on the heavily loaded substantially conical cam means, bearing means and piston means.

2. The reciprocating means recited in claim 1 having positioning means mounted on said housing means and engageable with said cam means for positioning said cam means in a desired position eccentric with respect to said barrel means and said shaft.

3. The reciprocating means recited in claim 2 wherein said positioning means is operable to lock said cam means in said desired position.

4. The reciprocating means recited in claim 1 wherein said rolling means comprises a ball.

5. The reciprocating means recited in claim 1 wherein said rolling means comprises a conical roller.

6. The reciprocating means recited in claim 1 wherein said cam means is provided with a cam surface, said cam surface comprising an internai conical surface.

7. The reciprocating means recited in claim 1 wherein said cam means is provided with a cam surface, said cam surface comprising an external conical surface.

8. The reciprocating means recited in claim 1 wherein said cam means is provided with a cam surface, said cam surface comprising a convex arcuate surface.

9. The reciprocating means recited in claim 1 wherein said cam means is provided with a cam surface, said cam surface comprising a concave arcuate surface.

10. The reciprocating means recited in claim 1 wherein said cam means comprises a thrust plate provided with an internal conical cam surface and a bearing means pro vided with a straight cam surface.

11. The reciprocating means recited in claim 1 wherein said cam means comprises a thrust plate provided with an external conical cam surface and a bearing means provided with a straight cam surface.

12. The reciprocating means recited in claim 1 wherein said cam means comprises a thrust plate provided with an external conical cam surface and a bearing means provided with an internal conical cam surface.

13. The reciprocating means recited in claim 1 wherein said cam means comprises an internal thrust plate pro vided with a straight cam surface and an outer bearing means provided with an internal conical cam surface.

14. The reciprocating means recited in claim 1 wherein said cam means comprises an internal thrust plate pro vided with an external convex arcuate cam surface and outer bearing means provided with an internal convex arcuate cam surface.

15. The reciprocating means recited in claim 1 wherein said cam means comprises an internal thrust plate provided with an external concave arcuate cam surface and outer bearing means provided with an internal concave arcuate cam surface.

16. The reciprocating means recited in claim 1 wherein said cam means comprises an internal thrust plate provided with an external conical cam surface and bearing means provided with an internal conical cam surface.

17. The reciprocating means recited in claim 1 wherein said rolling means is carried by said piston means.

References flirted in the file of this patent UNITED STATES PATENTS 2,069,651 Ferris Feb. 2, 1939 2,769,393 Cardillo et al. Nov. 6, 1956 2,997,962 Wysong Aug. 29, 1961 FOREIGN PATENTS 550,917 Germany Mar. 22, 1931 

1. FOR A FLUID DEVICE HAVING HOUSING MEANS, A SHAFT ROTATABLE WITH RESPECT TO SAID HOUSING MEANS, BARREL MEANS DISPOSED ABOUT SAID SHAFT, AND PISTON MEANS RECIPROCABLE IN SAID BARREL MEANS, RECIPROCATING MEANS FOR RECIPROCATING SAID PISTON MEANS IN SAID BARREL MEANS SAID RECIPROCATING MEANS COMPRISING; (A) CAGE MEANS DISPOSED ADJACENT ONE END OF SAID PISTON MEANS AND CONNECTED TO SAID BARREL MEANS, (B) SUBSTANTIALLY CONICAL CAM MEANS ADJACENT SAID CAGE MEANS FOR RECIPROCATING SAID PISTON MEANS IN SAID BARREL MEANS, (C) BEARING MEANS DISPOSED ABOUT SAID SHAFT AND ROTATABLE WITH RESPECT THERETO, (D) SAID CAGE MEANS, SAID SUBSTANTIALLY CONICAL CAM MEANS, SAID BEARING MEANS AND SAID PISTON MEANS DEFINING A CAVITY, (E) SAID SHAFT BEING OPERATIVELY ASSOCIATED WITH ONE OF SAID BARREL MEANS AND SAID SUBSTANTIALLY CONICAL CAM MEANS TO CAUSE RELATIVE ROTATIVE MOVEMENT BETWEEN SAID BARREL MEANS AND SAID SUBSTANTIALLY CONICAL CAM MEANS, AND (F) ROLLING MEANS IN SAID CAVITY IN ROLLING CONTACT WITH SAID BEARING MEANS AND SAID SUBSTANTIALLY CONICAL CAM MEANS THEREBY SUBSTANTIALLY ELIMINATING SLIDING FRICTION ON THE HEAVILY LOADED SUBSTANTIALLY CONICAL CAM MEANS, BEARING MEANS AND PISTON MEANS. 